Assault Weapons , When a gunman armed with an assault rifle and carrying more than 100 rounds of ammunition shot and killed a Transportation Security Administration officer at Los Angeles International Airport on Nov. 1, 2013, the event represented the latest in a series of incidents involving such weapons. On Dec. 14, 2012, a perpetrator had walked into Sandy Hook Elementary School, Newtown, Conn., armed with two semiautomatic handguns and a Bushmaster AR-15 semiautomatic rifle; he used the latter to shoot and kill 26 students and teachers. Earlier that year 12 people were murdered and 58 were injured in an Aurora, Colo., movie theatre by a person wielding a .223-calibre AR-15. Other recent high-profile mass murders (defined as the murder of four or more victims in a single incident) that involved the use of semiautomatic handguns included the shooting in Tucson in 2011 of U.S. Rep. Gabrielle Giffords of Arizona (six bystanders were killed) and the 2007 Virginia Tech massacre, which claimed the lives of 32 victims. In the wake of these events, Democrats in the U.S. Senate (with the support of Pres. Barack Obama) proposed measures to limit the availability of assault weapons (AWs) and high-capacity (more than 10-round) magazines. Though the Senate measures failed to pass on April 17, 2013, similar initiatives were signed into law in the states of New York, Connecticut, Colorado, and Maryland.

A Rhode Island State Police officer exhibits the high-capacity magazines of an AR-15 semiautomatic …

Steven Senne/AP Images

Defining Assault Weapons

The definition of what constitutes an assault weapon varies, often as a function of the current political debate. The Gun Control Act of 1968 defined the profiles of individuals who were allowed to own a firearm and the regulatory process for obtaining a federal firearm license (FFL). Individuals who purchased a fully automatic weapon were required to obtain a Type III FFL prior to a purchase (a stipulation that had been required for the purchase of an automatic weapon since the National Firearms Act of 1934). Semiautomatic weapons (those that fired one round per trigger depression) could be purchased from federal firearm licensees, from an unlicensed dealer, or through a private transaction. Under the Brady Handgun Violence Prevention Act of 1993, the U.S. attorney general established (1998) a National Instant Criminal Background Check System (NICS) to prohibit the sale of firearms to felons, fugitives, those identified as mentally incompetent, and others identified as banned from gun ownership. Members of these groups, however, often acquired guns from someone other than a licensed dealer and thus avoided the NICS.

On June 27, 2013, days before legislation prohibiting the sale of high-capacity magazines took …

The 1994 Assault Weapons Ban placed limits on the sale of semiautomatic weapons from any source. That legislation defined an AW as a semiautomatic that had two “military-style” features, which included a flash suppressor, a bayonet mount, a threaded barrel, a folding stock, a pistol grip, and a high-capacity detachable magazine. Critics argued that these features made a weapon “military-like” but that they were unrelated to the qualifications that actually made a weapon an AW—the capacity to fire large numbers of rounds in short order. Critics contended that it was the latter that needed to be controlled and that the military features were mainly cosmetic for civilian guns.

The purpose of the two main provisions of the bill was to ban firearms with at least two military-style features and to enact a ban on large-capacity magazines (LCMs). Prior to the enactment, military-style assault weapons were rarely recovered from street crimes: the average 1–6% recovery rate remained the norm. It is therefore important to separate the expected effects of the two main provisions of the 1994 law. The provision to limit military-style firearms was intended to reduce harms associated with law-enforcement-officer-involved shootings, which disproportionately involve AWs and to reduce the number of rounds fired in mass shootings. The provision to ban LCMs was intended to have a more direct impact on street crimes.

Because the military-style features were in part cosmetic, manufacturers of the weapons could alter their appearance to comply with the federal legislation without affecting the weapons’ functionality. The Tec-9 was specifically banned in California after Patrick Edward Purdy used a semiautomatic rifle to murder five schoolchildren at a Stockton elementary school on Jan. 17, 1989, and was also specifically banned in the 1994 federal legislation. The manufacturer (Intratec) removed the threaded barrel and barrel shroud, reduced the magazine capacity, and continued to legally manufacture an otherwise identical weapon after the federal ban. The AW ban was not renewed when it expired in 2004.

Research on the Assault Weapons Ban

The main source of data on the effectiveness of AW bans came from research conducted on the 1994 federal assault weapons ban. In 1997 and in a follow-up in 2004, criminologists Christopher S. Koper, Jeffrey A. Roth, and Daniel J. Woods (only in 2004) published the results of two federally funded studies of that ban. The first study included data for only a short period after the federal legislation was in place and did not find an effect of the law. The researchers noted that this was not prima facie evidence of the ineffectiveness of an assault weapons ban, but the 1994 legislation contained numerous provisions that greatly limited its scope. All weapons subject to the ban that were manufactured prior to the ban could be legally possessed, including firearms imported into the U.S. after the ban was in effect. Additionally, during the period when the legislation was debated but was not yet in effect, abnormally large numbers of these types of weapons were purchased. Thus, the researchers concluded that there was little immediate effect on the number of these weapons in circulation.

The second study, which was released as the assault weapons ban was set to expire in 2004, showed much larger effects. Six measures were used to examine the effects of the ban, three each for the weapons ban and the ban on LCMs. The researchers tested whether prices for banned weapons and magazines increased and whether the number produced decreased, to estimate whether the supply declined. They reviewed Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) data on weapons recovered from crime scenes to determine if the share of banned weapons and magazines declined. They also considered whether the number of shots fired and the number of homicides declined.

Major Findings on Assault Weapons

Koper, Woods, and Roth found that the ban did not affect the price or supply of assault rifles, but the prices of assault pistols were increasingly higher than those of comparable handguns, and the production of assault pistols declined much faster than that of comparable handguns. The number of AWs recovered by law enforcement declined substantially between 1992–93 and 2001–02 (from 5.4% to 1.6% of recovered weapons that were traced, a drop of 70%). Additionally, data from six cities found declines in the percentage of recovered AWs, ranging from 17% to 72%.

Other Outcomes

Prices of LCMs for assault pistols increased 80% from 1993 to 1998, although prices for LCMs associated with assault rifles were similar in 1993 and 1998. Sufficient data on the number of LCMs recovered from crime scenes before and after the ban was available only from two cities. In the period after the law was put into effect, LCM handgun recoveries declined 16% in Anchorage, Alaska, and total LCM gun recoveries declined 24% in Baltimore, Md. The researchers also found that in mass shootings, the number of rounds discharged declined by almost half, from 29 to 15. The assault weapons ban also reduced harms associated with law-enforcement-officer-involved shootings. Finally, researchers found that crimes involving the discharge of rounds from LCMs were more likely to result in a criminal victimization.